Insulating a greenhouse - advice sought.

JohnB · Post by **JohnB** » 09 Nov 2010, 11:58

featherstick wrote:You could give it a go. This chicken-greenhouse is one of those permaculture ideas that seem to keep circulating but that no-one has ever tried out.

A number have been tried, and I've seen some stuff on the web, but I haven't come across any detailed research.

sam_uk · Post by **sam_uk** » 09 Nov 2010, 12:29

JohnB wrote:
featherstick wrote:You could give it a go. This chicken-greenhouse is one of those permaculture ideas that seem to keep circulating but that no-one has ever tried out.
A number have been tried, and I've seen some stuff on the web, but I haven't come across any detailed research.

No nor me, I did find this;

"I've done this for many, many years and it is great.
Be sure to have vents both low and high. Sulpher Hexafluoride is heavier than air and methane gas is lighter than air. If these build up too high can cause damage to your plants and birds/yourself." http://forums2.gardenweb.com/forums/loa ... 10146.html

RenewableCandy · Post by **RenewableCandy** » 09 Nov 2010, 13:36

Erm...where does the Sulphur Hexafluoride come from? (tries to imagine chickens brushing their teeth...)

Post by **kenneal - lagger** » 09 Nov 2010, 14:58

mikepepler wrote:We gave an award in 2009 to GERES for develoiping a solar greenhouse in the Himalayas. Worked quite well by all accounts, especially considering how cold it gets there!
http://www.ashdenawards.org/winners/GERES09

That's a brilliant idea, Mike. You would have to provide extra light in the winter in the UK, though. The light levels in the Himalayas must be pretty constant throughout the year.

Add that to the project list.

JohnB · Post by **JohnB** » 09 Nov 2010, 15:18

kenneal wrote:That's a brilliant idea, Mike. You would have to provide extra light in the winter in the UK, though. The light levels in the Himalayas must be pretty constant throughout the year.

Add that to the project list.

I've often wondered why greenhouses have glass on the north side, rather than a wall with thermal mass. Maybe the lack of sun could be compensated for by including some some hot beds and other simple ideas discussed here.

Post by **kenneal - lagger** » 09 Nov 2010, 15:40

JohnB wrote:Maybe the lack of sun could be compensated for by including some some hot beds and other simple ideas discussed here.

The length of time light is received has a big influence on plant growth. Although Scotland is much colder than England they get good growth there because the length of day light is longer.

Once a temperature of over, I think it is, 6degC is achieved most plants will grow but only for the hours of daylight which can be as low as 6 hours on a wet, wintry day. If you can extend the lit period you will get much more growth.

woodburner · Post by **woodburner** » 09 Nov 2010, 17:51

kenneal wrote: We're talking about a greenhouse here and the ability to grow a bit of extra food. You would need some pretty expensive, both in monetary and carbon terms, kit to generate temperatures over 100C.

Not so. It needs only a collector panel and a recirculating fan. The sun can get a black panel to well over 100ºC, and the rock will store the heat at something less than the panel. You just have to limit the maximum temperature to the lowest rated component.

Neily at the peak · Post by **Neily at the peak** » 09 Nov 2010, 22:26

My father's greenhouse is doubled glazed with a red brick cavity wall on the north side, it is essentially a lean-to conservatory without the concrete floor, he is in Lincolnshire and from memory I think he said that it never got below 47 deg f last winter, I will check next time I speak with him.

Neil

Catweazle · Post by **Catweazle** » 09 Nov 2010, 23:21

I can't build a wall inside the north end, the paving slabs are only on sand and would never support it. I could put in foil covered foam insulation boards there, to reflect light back into the greenhouse floor and stop heat loss through that glass, perhaps a slight curve on the board would focus the heat onto a water butt thermal store.

I love the greenhouse in Mikes link, maybe it would be cheaper if the North end was dug into a hill instead of built with bricks, with a bit of clever piping you could have the run-off watering the plants automatically.

emordnilap · Post by **emordnilap** » 10 Nov 2010, 10:22

There's probably a diy way of circulating water from a black rainwater tank through plastic water pipes (it's called 'Hydrodare" here), a bit like the idea of a coil of black pipe in the sun can provide a shower. Some of the piping could be laid underneath the ground in the polytunnel, like under-floor heating.

Worth a few minutes' thought, perhaps, so if people have any ideas fire away. We're getting a polytunnel around February/March, depending upon the weather and would seriously consider putting some pipe underground first.

I, ermmm, 'found' a hundred-metre roll of inch-and-a-half Hydrodare near where I work. I kept my eye on it for a year or so and then thought, "This needs putting somewhere safe in case someone steals it."

Would one of these be any use for very slow pumping of water?

the mad cyclist · Post by **the mad cyclist** » 10 Nov 2010, 12:59

Slightly off topic.
In another thread we discussed how modern cheap mass produced items are unreliable, well the small 12v DC fan that I fitted into the pipe leading from the apex of my greenhouse to the heat store below, has now been running almost constantly for three and a half years.
Not bad to say it cost approximately £3.

emordnilap · Post by **emordnilap** » 10 Nov 2010, 13:08

A pound a year.

Sound like a Chinese wage.

the mad cyclist · Post by **the mad cyclist** » 10 Nov 2010, 15:46

emordnilap wrote:A pound a year.

Sound like a Chinese wage.

When I were a lad, you could go round world for a pound and when yer got back, you could still buy 10 woodbine und fish and chips with change.

CountingDown · Post by **CountingDown** » 10 Nov 2010, 20:25

the mad cyclist wrote:Slightly off topic.
In another thread we discussed how modern cheap mass produced items are unreliable, well the small 12v DC fan that I fitted into the pipe leading from the apex of my greenhouse to the heat store below, has now been running almost constantly for three and a half years.
Not bad to say it cost approximately £3.

That sounds like an interesting project - I've been looking at something like this to moderate the summer temp in our Polytunnel. Have you got more details? Presumably it's solar-powered?

CountingDown · Post by **CountingDown** » 10 Nov 2010, 20:36

Just been reading thru the whole thread. Lots of interesting stuff. I've been considering something to heat our polytunnel made from an old radiator, connected to a solar-powered pump, with (plastic?) pipes running under the brick floor to add some heat to keep it warm overnight.

I have a vague memory of a CAT flyer with something like this on. Time to search the internet!